Antimicrobial peptides generally exhibit broad antimicrobial spectra and are considered unlikely to develop drug-resistant microorganisms. Thus, their expected uses include prevention or treatment of bacterial infections in humans and animals as well as provision of antimicrobial properties to products such as food, etc. To date, many antimicrobial peptides have been isolated from various animals and plants (e.g. Patent Documents 1, 2). There have been reported some synthetic antimicrobial peptides designed and synthesized based on known amino acid sequences whose relevance to antimicrobial activities had never been discussed (Patent Document 3).